Voltage regulation and supply



Dec. 26, 1950 D. K. FROMAN 2,535,355

I VOLTAGE REGULATION AND SUPPLY Filed Dec. 8, 1944 kwa ied .fl-C Rulerw/ r/msm. INVEN TOR.

BDyarol if Froman Patented Dec. 26, 1950 VOLTAGE REGULATION AND SUPPLYDarol K. Froinan, Denver, 0010., assignor to the United States ofAmerica as represented by the United States Atomic Energy CommissionApplication December 8, 1944, Serial No. 567,285

Claims.

1 This invention relates to voltage regulating systems and moreparticularly to power supply circuits delivering a constant potential bymeans of electronic regulation. Power supplies of the type referred togenerally include an electron discharge device placed in series betweenthe supply circuit and the load. The space current conductivity of thedischarge device is varied when there is a tendency for a change ofvoltage at the terminals of the load circuit or in the supply circuit.The conductivity variation is compensative to maintain current flow inthe load circuit at such value which provides a substantially constantterminal voltage. The type of control used for the discharge deviceplays an important part in the overall response of the system. Variouselectronic control circuits have been developed for effecting regulationof the series connected discharge device.

A particular feature of this invention is that the control circuitpermits greater flexibility of regulation as well as stability in theoperation of the supply circuit.

Another feature of this invention is that th control circuitincorporates circuit elements heretofore not 'used, which applied in aspecific manner result in a manyfold increase in the controleffectiveness of the system.

A particular advantage of the control circuit is that small variationsin the output voltage of the supply can be effectively compensated.Moreover, use can be made'of amplifiers having extremely highamplification.

Another advantage of the invention is that increased stability ofoperation results from the fact that the control voltage for thecontrolled tube, derived in part from a vacuum tube as an impedanceelement, is not affected by terminal voltagevariations except in thepredetermined and desired manner.

The invention contemplates the use of an electrical network inconnection with the control electrode of the controlled tube. At leastone impedance element of the network is a vacuum tube. The inventionalso provides a circuit in which the controlled voltage for thecontrolled tube is derived from a cathode-follower. The latter isenergized from a suitable amplifier and is simultaneously utilized tofur nish a constant potential operating voltage for certain electrodesof the vacuum tube in the amplifier.

Other features and advantages will be .ap- '7 parent from the followingdescription of the invention, defined in particularity in the appendedclaims, and taken in connection with the accompanying drawing in which:

Figure l is a simplified circuit diagram of the control circuit andFigure 2 isa schematic circuit diagram of a complete supply systemincorporating the control circuit.

Referring to Figure l, the input to the control circuit is taken from apower supply indicated by a block diagram marked Rectified AC PowerSupply. The purpose for this is to illustrate the fact that any desiredtype of supply may be'used, including either a full wave or a half waverectifier and conventional filter networks. The direct current output ofthis sup-' ply is applied between terminals A and B at the indicatedpolarity. The output side of the supply system is provided withterminals C and D to which a load circuit may be connected. The controlcircuit maintains across these terminals a substantially constantpotential irrespective of changes in the load or fluctuations in thesupply circuit within predetermined limits. The vacuum tube l is aseries connected discharge device having its anode 2 connected to thepositive terminal of the supply and the cathode 3 to the positiveterminal of the load circuit. The current flow through the tube 1 isregulated by means of the bias voltage applied to the control electrode4. The latter connects to a junction point between the resistor 5 andthe cathode 6 of the vacuum tube 1. The anode 8 thereof connects to thecathode 3 of the tube l and thereby also to the positive terminal of theload circuit. The other terminal of the resistor 5 connects to thecommon negative side of the supply and the load circuit. This side isgrounded in the majority of cases and, therefore will be referred to asground.

Observing this circuit, it will be seen that the vacuum tube 1 and theresistor 5 in series form a voltage divider across the output of thesupply system. The space current path of the tube 1 is also directlyconnected between thecontrol electrode 4 and the cathode 3 of the tubeI. Consequently, this tube replaces the conventional grid resistor andperforms the function of a variable impedance path in the grid circuitof the controlled tube I. Looking at this circuit from another angle, itwill be apparent that the vacuum tube 1 with the resistor 5 isessentially 'a degenerative vacuum tube circuit, known in the art as acathode-follower. Its high input impedance and low output impedance isadvantageously used as a coupling means between the controlled tube andthe amplifier control circuit.

By the use of the cathode-follower it is feaslble to employ an amplifieroi the dynamic load resistance type and benefit from the very high gainthat such amplifier possesses. The tube II by virtue of its connectionin the circuit operates as the dynamic anode load resistance of theamplifying tube I2. In order to perform this function properly, it isessential that a substantially constant potential be maintained betweenthe cathode l3 and the screen grid electrode [4 of this tube. Asecondary function of the oathode-follower I is to furnish the screengrid potential in the manner described in my copending applicationSerial No. 558,423 filed October 12, 1944, now Patent No. 2,517,863,issued August 8, 1950.

The amplifying vacuum tube I! has the cathode l5 as well as thesuppressor grid l6 connected to ground. In the input circuit of theamplifier the grid l1 connects through a source of fixed potential,shown here by way of example, by the battery IE to the variable tap ofthe potentiometer Ill. The latter is in series with a fixed resistance2| between the output terminals of the load circuit. The screen gridelectrode 22 connects to the junction point between potentiometer I9 andthe resistor 2|. It is to be noted that under cetrain conditionsgoverned by the value of output voltage it may be necessary to connectother resistance elements in series across the supply circuit inaddition to the-resistance shown here in order to obtain the requiredscreen grid and control grid potentials.

The output circuit of the amplifier, as mentioned before, has for itsanode load resistance the vacuum tube II. The connection is effectedthrough the resistor 23 which interconnects the cathode I3 and the anode24. The purpose of this resistor is to supply the minimum bias potentialfor the grid electrode 25 which return returns to the anode terminal ofthe resistor 23.. The suppressor grid 28 terminates at the cathode'l3 inthe conventional manner. The screen grid M of the tube I I connectsdirectly to the junction point of the resistor 5 and the cathode 6 orthe cathode-follower tube I. The grid circuit of the latter,.inc1udingthe grid electrode 21 returns to the cathode I3 through a source offixed potential, shown here by way of example, by the battery 29.

The operating voltages in various portions of the circuit are so chosenthat the current flowing in the output circuit through the controlledtube I produces the required voltage drop in the load circuit. Thestatic operating potentials maintain this value of current and theconductivity characteristic of the tube l is altered only when there isa change which tends to alter the voltage out put, for example, when theload increases or decreases, or when the direct current input to thecontrol system fluctuates for any reason at all. The static potentialfor the grid circuit of the controlled tube I is derived from the anodecur-' words, the value of the source is so calculated as to maintain thegrid 21 with respect to the cathode 6 at a potential which provides therequired 4 current fiow to furnish the static bias potential of the grid4. The value of the battery voltage is approximately that of therequired screen grid potential for the vacuum tube II. In practice. thisbattery may be replaced by a suitable electronic supply source or by anumber of series connected primary cells, of the type known in the artas bias cells.

In the input circuit of the amplifier the battery l8 furnishes apotential known as the reference voltage. This is a constant andvariations in the output voltage of the system are applied to theamplifier with respect to this reference voltage. In other words, thebattery I8 maintains the required bias potential for the control grid llof the amplifier tube I! so that the potential at the cathode l3 willproperly energize the cathode-follower to have the required currentconductivity. Once this static condition is established extremely smallvariations in the output voltage determined by the setting of thepotentiometer l9 will be impressed on the control grid ll. Thesevariations in an amplified form appear at the cathode l3 .and areimpressed, additively' or subtractively as to the fixed potential of thebattery 29 and cause a change of current in the cathode-follower whichwill correspondently change the conductivity ofthe controlled tube I.Since the cathode-follower follows the potential variations of thecathode I3,.

rtial therefore varies in phase with the cathode potential andconsequently, is maintained substantially constant with respect to thecathode I3. This is instrumental in the function of the vacuum tube IIas the dynamic load resistance for the vacuum tube l2. g

Referring to Figure 2 the voltage regulator is shown applied to a supplysystem which derives all operating potentials from the supply ings. Forthe sake of simplicity the primary winding which would form a filamenttrans- The operation of the control system is essentially the same asthe one described in connection with Figure 1. Therefore, identicalcircuit elements appearing here are marked with similar referencecharacters bearing primary indices. between the load circuit marked byterminals C and D and the rectifier output circuit marked by terminals Aand B. The anode 2" connects to the cathodes of the rectlfiers 33 and 35whereas the cathode 3 connects to the positive side of the load circuit.The cathode-follower comprising the vacuum tube and the resistor 5' isin shunt with the load circuit. The anode 8 is connected to the positiveside and the oath- The vacuum tube I is placed in series ode 6' to theresistor The amplifier control circuit for the cathode-follower includesthe resistance tube II and the amplifying vacuum tube 12'. The cathodel3 connects to the anode 24' through the resistor 23'. The control grid25' returns to the anode 24' and the suppressor grid 26'. to the cathode[3. A by-pass condenser 31 shunts the resistor 23'. In the input circuitof the amplifier the fixed potential for the bia of the grid I1 isderived from the glow tube 38 and the resistor 39 in parallel therewith.The suppressor grid I6 returns to the cathode l5. The glow tube 38 isenergized by the space current of the amplifying tube [2' and maintainsa. uniform voltage drop. The grid ll connects to the potentiometer 19'in series with a grid resistor 40. The potentiometer I9 is a portion ofa voltage divider comprising suitable resistance elements indicated bythe resistors 2|; 4|, 42, and 43. amplifying tube l2 derives operatingpotentials from the junction point of resistors 4| and 42.

The filaments of vacuum tubes 1' and H are energized from a commonwinding the center tap of which is connected to the cathode 6' of vacuumtube 1'. The cathode 6 is also connected to the grid 4" of the tube I aswell as to the screen grid I4 of the tube H in the same manner asdescribed in connection with Figure 1.

Resistor 46 included in this circuit functions as r operating conditionbefore others and may give 5 a large output voltage damaging the load.The grid current limiting resistor 46 prevents this. The control grid21' of the cathode-follower I returns to the cathode l3'- through aseries of bias cells 4| connected in the polarity shown here. The numberof cells shown is not intended to be representative of the voltage valueused. This will differ widely, depending upon circuit and vacuum tubeconstants. The filament 48 of the amplifying vacuum tube [2' isenergized from the winding 49, the center tap of which connects to thecathode IS.

The operation of the circuit of Figure 2 does not diiier materially fromthat of Figure 1. Under static conditions the vacuum tube I has aninternal resistance which permits current fiowin the load circuit of avalue producing the required output voltage. Very small changes in thisvoltage appearing across the potentiometer I! are applied to the inputcircuit of the amplifier tube l2" and are transmitted in an amplifiedform as changes of grid bias of the cathode-follower I. This in turnchanges the operating bias of the grid 4 controlling the internalresistance of the tube I in the manner to compensate for the changewhich tend to alter the output voltage.

What is claimed is:

l. Ina voltage regulating system, a supply circuit, a load circuit, avariable resistance electron discharge device having at least a cathodeand control electrode interposed therebetween for controlling thevoltage of said load circuit, a second discharge device and a resistancein series connected between terminals of said, load circuit, meansconnecting the junction between said second discharge device andresistance to said control electrode whereby said last-mentioneddischarge device operates as a cathode-follower, an electricalconnection between the anode of the The screen grid 22' of the saidcathode-follower and the cathode of said first discharge device, circuitmeans for varying the resistance of said cathode follower in accordancewith voltage variations of said load circuit, whereby the eflectiveresistance of said first discharge device is varied in accordance withthe voltage on the cathode of said cathodefollower. r

2. In a voltage regulating system, a supply circuit, a load circuit, avariable resistance electron discharge device having at least a cathode,anode, and control electrode and having the interelectrode space thereofelectrically connected in series with the supply circuit and the loadcircuit for controlling the voltage of said load circuit, a seconddischarge device having anode, cathode, and a control electrode, aconnection between the anode of said second device and an electricalterminal of said load circuit and' a connection including a resistorbetween said cathode of said second device and the other terminal ofsaid load circuit, circuit means connecting the junction between theresistance and the cathode of the second discharge device to the controlelectrode of the first discharge device, circuit means connecting theanode of the second discharge device to the cathode of the firstdischarge device, whereby said second discharge device operates as acathode-follower, and whereby the effective resistance of said firstdischarge device is varied in' accordance with the variations of voltageoutput of said cathode-follower, circuit means for controlling thevoltage of the cathode with respect to the anode of saidcathode-follower in accordance with voltage variations of said loadcircuit including an amplifier having input and output circuits, circuitmeans for impressing the voltage output of said output circuit on thecontrol electrode of said cathode-follower, and circuit means forimpressing voltage variations in said load circuit on the input circuitof said amplifier.

3. In a voltage regulating system including a source of energy and aload circuit, a variable V resistance electron discharge device havingat least a cathode and control electrode interposed therebetween forcontrolling the voltage of said load circuit, an amplifier having aninput and output circuit, an amplifying vacuum tube and asecond vacuumtube electrically connected to the first tube so as to operate as thedynamic load resistance of said first tube, a second electron dischargedevice and a resistance connected in series therewith connected betweenterminals of said load circuit, circuit means connecting said seconddevice as a cathode-follower with respect to the control electrode ofsaid first device and as a cathode-follower with respect to the screengrid electrode of said second tube to supply a predetermined 'potentialthereto, circuit means for impressing voltage changes in said loadcircuit on the input circuit of said amplifier, circuit means includinga source of bias potential connecting the output circuit of saidamplifier with the control electrode of said cathode-follower and withthe cathode of said second tube.

4. In a voltage regulating system, a supply circuit, a'load circuit, avariable resistance electron discharge device having at least a cathode,anode, and control electrode and being electrically connected in serieswith the supply circuit and the load circuit for controlling the voltageof said load circuit, a second discharge device having anode, cathode,and a control electrode, a connection between the anode of said seconddischarge device is varied in accordance with the variations of voltagedeveloped between the cathode and anode of said cathode-follower,circuit means for controlling the voltage across said cathode-followerin accordance with voltage variations of said load circuit, including anamplifier comprising an input and output circuit, an amplifying vacuumtube and a second vacuum tube adapted to operate as the dynamic loadresistance of said amplifying tube, a circuit including a bias sourceconnecting the control electrode of said cathode-follower and thecathode of said second vacuum tube, a connection between the cathode ofthe cathode-follower and the screen grid electrode of said second tube,and

circuit means for impressing voltage variations in said load circuit onthe input circuit of said amplifier.

5. In a voltage regulating system, a supply circuit, a load circuit, avariable resistance electron discharge device having at least a cathode,anode, and control electrode, said discharge device being connected inseries with the supply circuit and the load circuit for controlling thevoltage 01' said load circuit, a second discharge device having anode,cathode, and a control electrode, a connection between said anode ofsaid second device and a terminal of said load circuit and a connectionbetween said cathode of said second device and the other terminal ofsaid load circuit including a resistance, circuit means connecting thejunction between the resistance and the cathode of the second dischargedevice to the control electrode of the first discharge device, andcircuit means connecting the anode of the second discharge device to thecathode of the first discharge device, whereby said second dischargedevice operates as a cathode-follower, and whereby the eflectiveresistance of said first discharge device is varied in accordance withthe variations of voltage developed between the anode and cathode 01said cathode-follower, circuit means for controlling the voltage acrosssaid cathode-follower in accordance with voltage variations of said loadcircuit, including an amplifier comprising an input and output circuit,an amplifying vacuum tube and a second vacuum tube adapted to operate asthe dynamic load resistance of said amplifying tube, a circuit includinga bias source connecting the control electrode of said cathodefollowerand the cathode of said second vacuum tube, said bias source supplying apotential at the value of which said cathode-follower is controlled inaccordance with variations of the potential of the cathode of saidsecond tube, a connection between the cathode of the cathode-followerand the screen grid electrode of said second tube, and circuit means forimpressing voltage variations in said load circuit on the input circuitof said amplifier.

DAROL K. FROMAN.

l REFERENCES crrEn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 1 Number lflame Date 2,075,966 Vance Apr. 6, 19372,120,884 Brown June 14, 1938 FOREIGN PATENTS Number Country Date214,985 Switzerland Aug. 16, 1941

